I'm not denying Trump's great accomplishments -- I'm one of his biggest fans -- but I agree with Mencken that he's also succeeding because he knows how to influence all the voters, not just the political elite and intelligentsia.
Demagoguery is an appeal to people that plays on their emotions and prejudices rather than on their rational side. Demagoguery is a manipulative approach often associated with dictators and sleazy politicians that appeals to the worst nature of people.
Explain what is irrational about Trump’s campaign issues.
Note, Reed rejected Wilson's League a full week before any Republican joined him (Borah, was the first); and as the Mencken piece makes clear, was really the master debater who more than any other destroyed the Wilsonian fallacy.
Reed was also an advocate of a strong Navy, and predicted the course of the Japanese attack in the Pacific in 1922, in opposing the Naval disarmament treaty.